Case Studies In Small Animal

Cardiovascular Medicine

Home Up .    Radiographs ECG 2D Echo M-Mode Color Flow Doppler Diagnosis

Case 9

M-Mode Echocardiograms

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This M-mode echocardiogram was guided by the two-dimensional echocardiogram to ensure that the M-mode cursor was perpendicular to the walls of the left ventricle and that the cursor was placed in the middle of the chamber, between the two papillary muscles. The dog's breathing was stopped for a few seconds to stop respiratory artifact. Measurements of the left ventricle (LV) were taken. As shown, the left ventricular end-diastolic diameter (EDD) was 4.2 cm in this dog. Normal for this dog is approximately 3.0 cm. The end-systolic diameter (ESD) was 2.4 cm (normal = 2.0 cm). This meant that the walls moved 1.8 cm closer to each other from the end of diastole to the end of systole. This is an increase in wall motion for this size dog. The other way to measure wall motion is to calculate the percent change in diameter from the end of diastole to the end of systole (i.e., the shortening fraction). It is also increased and is calculated using the formula EDD - ESD/EDD (see the Quiz below). The increase in wall motion can be subjectively appreciated by noting that the excursion of the interventricular septum (between the RV and LV) is greater than normal. Free wall motion appears to be normal. Left ventricular wall thicknesses (interventricular septum and left ventricular free wall) were normal (8 mm). 


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This M-mode echocardiogram was taken with the beam crossing the mitral valve. Mitral valve excursions are labeled in alphabetical order. "A" is the peak of maximum opening that occurs with atrial systole, late in diastole. There usually is no "B". "C" is the point where the leaflets close at the onset of systole. "D" is the point just before the mitral valve leaflets open at the onset of diastole. "E" is the maximum opening of the leaflets during rapid ventricular filling in early diastole. "F" is the nadir between "E" and "A". The distance between the E point and the interventricular septum (E point to septal separation or EPSS) is commonly measured as another index of left ventricular function. In this dog it is mildly increased to 6 mm (normal is approximately 3 to 4 mm for this size dog).


Correct Quiz



Mark D. Kittleson, D.V.M., Ph.D. All rights reserved.